Everyone knows that to be a successful TV detective you have to be grumpy, sexy and effortlessly cool. Would Morse, Taggart, Frost or Rebus and Wallander have risen through the ranks if they had been modest and wimpish?
Wouldn’t the county of Midsomer be an even more dangerous place if Detective Chief Inspector Tom Barnaby’s irascibility hadn’t been a deterrent?

Now there is Aurelio Zen, an enigmatic Italian detective with a sardonically-raised eyebrow, a nose for getting himself into trouble with his superiors and a fondness for ice cream and sharp suits. On the human side, he loves his old mum so much that, when his marriage broke up, he moved back in with her. Zen’s first appearance on TV last weekend — as personified in a splendid piece of type-casting by the deeply macho and down-to-earth Rufus Sewell — brought a huge ­reaction from viewers.

‘All those rough, loudmouth TV cops in their anoraks, cheap suits and egg-stained ties are going to have to tidy themselves up if they are to compete,’ was a typical online comment.

Sewell is thrilled to be allowed to wear modern dress after years of appearing in Shakespeare on stage and TV costume dramas, such as 'The Taming Of The Shrew', '­Middlemarch' and 'Charles II: The Power And The Passion'. ‘At the age of 43, I’m at last being allowed into the 21st century’, he says.

The renegade detective — down on his luck but too much of a macho anti-hero to admit it — is the creation of Wolverhampton-born author Michael Dibdin, who died in 2007. Dibdin wrote 11 Zen novels and was awarded the coveted Golden Dagger prize by the Crime Writers’ Association.

Three of the stories have been filmed for the current series and the rest are likely to be made over the next two years. The adaptations are likely to make as huge a TV star of Sewell as Sherlock has done for his friend Benedict Cumberbatch. ‘When I was sent the script, I wanted to know the answer to two questions before I read the first page,’ he says. ‘I asked if I could be just a little bit funny. They said I could be as tongue in cheek as I wanted.

‘I asked if Zen was like all those other TV cops who stride down corridors, kicking doors down and shouting at people and they said he wasn’t. From that moment, I was gung-ho.’

The stories are set in the stunning backdrop of Rome and most of the action takes place on the streets. ‘We filmed without people realising,’ says Sewell. ‘A lot of scenes were so public that we only had one chance to film. For one scene, I had to run through a crowd and a little old lady wandered into my path. I scooped her up in my arms, as if it was part of the story, and kept on running.

‘Eventually, when I put her back on her feet, we explained what had happened and she was fine, but I think other members of the public wondered if I was kidnapping her.’

In this week’s story, 'Cabal', the body of Umberto Ruspanti, a member of one of Rome’s most prominent aristocratic families, is found beneath a bridge in the early hours of the morning. Zen is assigned to the case by senior government officials who want him to conclude that it is suicide — even though they suspect that it is really murder.

Zen refuses to take part in a cover-up and comes under pressure to change his mind. When he realises that a powerful secret organisation called the Cabal may be responsible for Ruspanti’s death, he stubbornly digs his heels in even further.

At the same time, he is trying to balance all that pressure with the stirrings of romance with Tania Moretti, the chief’s new assistant played by Casino Royale Bond girl, Italian actress Caterina Murino. When she was asked what attracted her to the part, she had a two-word answer: ‘Rufus Sewell!’ In the flesh, the hollow-cheeked actor is a dapper man with a broad face and captivating green eyes. He is charismatic, cheerful and clearly got on extremely well with his beautiful leading lady.

In real life, Sewell married Australian fashion journalist Yasmin Abdallah in 1999, but they divorced a few months later. He then wed his second wife, Amy Gardner, and they have an eight-year-old son, Billy. However, the couple have since divorced. Sewell also had a liaison with Kate Winslet.

So, is it really goodbye to all those smouldering parts in thigh-hugging britches and billowing silk shirts?

‘Thank God, I’m getting ugly,’ he laughs. ‘Of course, I want to look good, as that helped me get jobs. But it didn’t get me the jobs I wanted and it held me back. I’ve even been stopped in the street by people who think I’m Lovejoy!

‘I had all this energy I couldn’t put into my parts, as people were asking me to sit still on a b****y horse. I was desperate just to play someone with a limp or a Latvian accent.

‘Given the choice between someone saying I was handsome in a role or ugly but good, I know which I’d choose. In 'Middlemarch', I felt I was only impersonating an attractive person. I couldn’t even get girls at school, as I was fat and not at all attractive. It’s nice when women fancy me, but I think I will only disappoint them so I prefer it if they don’t know who I am.’

So does he think there is competition now with his friend and rival Benedict Cumberbatch, who got rave reviews portraying the sleuth of Baker Street as a modern crime fighter in last year’s TV series?

‘Yes, definitely — bring it on!’ he laughs. ‘Benedict is a mate, but as I live most of the time in Los Angeles, I didn’t see his Sherlock until I caught up with it on the plane’s in-flight entertainment. It was so good. But as for most other TV cops, forget them! So many have the same kind of character.

‘I want Zen to be believable, as he’s got flaws and he’s not a winner. He’s a bit of an outsider. In fact, Zen isn’t a million miles from the real me — it’s one of the few times in my life I’m feeling really comfortable.